Fortune’s curated selection of tech stories from the last 24 hours. Sign up to get the round-up delivered to you each and every day.

* Gowalla finally made it official: The location-based service will shut down at the end of January with its founders headed off to Facebook to work on the social network’s recently-unveiled Timeline feature. The news was first reported last week by CNNMoney. (Gowalla Blog and CNNMoney)
* Why the European Commission is starting up an antitrust investigation of Apple (AAPL) and five major book publishers. (Fortune)
* A dissection of Research in Motion’s (RIMM) $485 million write-off “related to its inventory valuation of BlackBerry PlayBook tablets.” (Monday Note)
* Google’s overall share of the Web ad market continues to grow and lead the pack with nearly 44%. And though Facebook still remains a distant fifth behind Microsoft (MSFT), Yahoo (YHOO), and AOL (AOL), it’s the only other big Internet portal experiencing growth, too. (All Things D)
* Online shoppers have spent almost $19 billion so far this holiday season, due at least in part to retailers offering generous discounts and free shipping. (The New York Times)
* Researchers are designing computing architecture that will more closely resemble the human brain. (The New York Times)
* Starbucks’s mobile app seems to be a hit with customers. The coffee conglomerate has processed more than 26 million mobile payments since January, 6 million of which happened during the last 9 weeks. (VentureBeat)
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